This invention relates to a storage system that manages a database, and more specifically to a database reorganization method.
A DBMS (DataBase Management System) which manages a database is conventionally designed to raise the responsiveness of the database. On the other hand, the design of a storage space of storage or the like is such that its management is simplified as much as possible by, for example, keeping a storage space of a database in one location for a long period of time. The storage space of a DBMS gradually becomes disorganized as the system is operated for a long time. Being “disorganized” here means that the storage space has a fragmented space, an uncollected area, and a disproportioned space management configuration. The disorganized storage space lowers the responsiveness of the database, with the result that an unexpectedly large portion of the storage space is taken up.
Many existing DBMSs have software dedicated to solving disorganization of their storage space. The software defragments a fragmented space, collects an uncollected area, and makes the space management configuration better proportioned, to thereby bring the storage area back to its organized, ideal state. This processing is called “reorganization”.
An administrator of such DBMSs has to remedy lowering of database responsiveness and consumption of an unexpectedly large portion of the storage space by reorganization through the periodic use of the reorganization software.
An example of DBMSs that employ dedicated reorganization software is disclosed in JP 2004-199497 A. In this DBMS, when an access request from a host computer is a write request and data requested to be written is log information which shows the contents of database processing performed on a buffer of the host computer, a conversion table which shows the association relation between logical position information recognized by the host computer and information of a physical position in a primary storage device subsystem is used to convert position information contained in the log information into information of a physical position in the primary storage device subsystem. Data in a database area of the primary storage device subsystem that is indicated by the obtained physical position information is updated to reflect the log information, and the access request is sent to a secondary storage device subsystem.
Another example of DBMSs that employ dedicated reorganization software is disclosed in JP 2004-199498 A. In this DBMS, when an access request from a host computer is a write request, it is judged whether or not data requested to be written is log information which shows the contents of database processing performed on a buffer of the host computer so that, when the data requested to be written is judged to be the log information, a conversion table which shows the association relation between logical position information recognized by the host computer through database processing and information of a physical position in a storage device subsystem is used to convert position information contained in the log information into information of a physical position in the storage device subsystem. Data in a database area of the storage device subsystem that is indicated by the obtained physical position information is updated to reflect the log information.